Many commercial vehicles currently utilize suspension assemblies that can retract and thereby raise the axle of the axle/suspension system off the ground. Such suspension assemblies conventionally are known in the industry as lift axle suspensions. Lift axle/suspension systems usually are paired or grouped with non-lift axle/suspension systems on a vehicle, the latter of which are commonly referred to as primary axle/suspension systems. A majority of lift axle/suspension systems utilize one or more pneumatic air springs to raise or retract the axle/suspension system. Pneumatic air springs of that type typically are referred to as lift air springs and generally can be placed in a variety of locations relative to the axle/suspension system to accomplish the lifting function. Another set, usually a pair, of pneumatic air springs is utilized to lower or extend the axle/suspension system for assisting in supporting the vehicle load and are typically referred to as ride air springs.
Lift axle/suspension systems usually are retracted or raised when the vehicle load is less than the load capacity of the primary or non-lift axle/suspension systems or when greater vehicle maneuverability is required. A number of different types of pneumatic or electro-pneumatic systems can be employed to operate lift axle/suspension systems, depending on the application and customer requirements. The present invention can be utilized with most types of such operating systems and also generally can be used regardless of the location of the one or more lift air springs. Such systems operate by simultaneously, but independently, supplying pressurized or compressed air to the lift air springs and exhausting air pressure from the ride air springs when it is desired to retract or raise the axle/suspension system. Conversely, when it is desired to lower the axle/suspension system to support a load, air pressure is supplied to the ride air springs and simultaneously exhausted from the lift air springs.
Although such prior art operating systems accomplish their goal of raising and lowering the axle/suspension system, a number of drawbacks are inherent in those systems. More particularly, such prior art operating systems often suffer from low overall system air pressure and lack the ability to rapidly deliver pressurized air to the relatively large ride air springs. For example, every time the axle/suspension system is raised or lowered, air pressure from a set of air springs, either the ride air springs or the lift air springs, respectively, is exhausted to the atmosphere. This exhaustion or complete loss of a certain amount of compressed air significantly adds to the total air consumption of the vehicle and increases the demands on the vehicle compressor, which supplies such pressurized air. If the lift axle/suspension system, together with other air-consuming vehicle devices, such as the brakes, are operated repeatedly over a short period of time, demand for pressurized air can exceed the compressor capacity, making it unlikely or impossible for all of the devices to operate at full capacity. More importantly, insufficient air pressure in those devices can cause premature failure of axle/suspension system components, such as axles, beams, and even vehicle frame components, the primary cause of which is low air pressure in the axle/suspension system ride air springs.
Previous designs have reduced or eliminated the above-noted problems by integrating control of the lift and ride air springs rather than allowing them to operate completely independent of one another. However, such systems generally require two different air pressure sources to fill and exhaust the lift air springs and the ride air springs. The air pressure sources usually involve a regulated air pressure source and an unregulated air pressure source. Although the axle lifts are common in the industry, the control circuits used to direct such air pressure sources to control such suspensions have varied widely. Such previous pneumatic control circuits have been comprised of off-the-shelf or modified components bolted together and/or piped together to form a pneumatic circuit. This method of creating a pneumatic circuit is generally not cost-effective nor efficient and requires that the componentry be mounted in enclosures to protect the individual components from the environment and to consolidate the circuit.
It would be desirable to provide an integral apparatus or method that allowed for the cost-effective distribution of two different air pressure sources to efficiently fill and exhaust at least two volumes of air. It would also be desirable to create a distribution apparatus in a single integrated module that need not be contained in a separate and additional enclosure.